Non-volatile memory device and method of fabricating the same

ABSTRACT

A non-volatile memory device includes a tunnel oxide layer, a charge storage layer, a blocking insulating layer, and a gate electrode that are sequentially stacked, as well as an impurity diffusion layer in an active region at both sides of the gate electrode. The gate electrode crosses active regions between device isolation layers formed in a predetermined area of a semiconductor substrate, and an edge of the charge storage layer is extended to have a protruding part that protrudes from the gate electrode. In order to form a charge storage layer having a protruding part, a stack insulating layer including first to third insulating layers is formed in an active region between the device isolation layers formed in the substrate. A plurality of gate electrodes crossing the active region are formed on the stack insulating layer, and a sidewall spacer is formed on both sidewalls of the gate electrode. Using the sidewall spacer and the gate electrode, the stack insulating layer is etched to form a charge storage layer that protrudes from the sidewall of the gate electrode.

RELATED APPLICATION

[0001] This application relies for priority upon Korean PatentApplication No. 2001-37420, filed on Jun. 28, 2001, the contents ofwhich are herein incorporated by this reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to a method offabricating a semiconductor device. More specifically, the presentinvention is directed to a floating trap-type non-volatile memory devicethat stores data in a charge storage layer including one insulatinglayer by injecting charges, and to a method of fabricating the same.

BACKGROUND OF THE INVENTION

[0003] Non-volatile memory devices continuously hold data even when anexternal power is turned off. As the integration density of memorydevices increases, there is a need for reducing the area and verticalheight of a memory cell. Since a conventional floating gate typenon-volatile memory device has a floating gate, it is restrictive toreduce a vertical height of a memory cell. For that reason, a floatingtrap-type non-volatile memory device has been attractive as a candidateto overcome the above disadvantage in that charges can be stored in atleast one insulating layer without a floating gate.

[0004]FIG. 1 is a top plan view of a conventional floating trap-typenon-volatile memory device. A device isolation layer 11 is formed in apredetermined area of a semiconductor substrate to define an activeregion 13. A plurality of gate electrodes 30 cross the active region,and a charge storage layer 24 is intervened between the gate electrode30 and the active region 13. A sidewall spacer 36 is formed on asidewall of the gate electrode 30.

[0005]FIG. 2 through FIG. 5 are cross-sectional flow diagrams showingthe steps of fabricating a conventional non-volatile memory device,taken along a line I-I′ of FIG. 1.

[0006] Referring now to FIG. 2, a device isolation layer 11 is formed ina predetermined area of a semiconductor substrate to define activeregions 13. A stack insulating layer 18 and a gate conductive layer 20are formed on a semiconductor substrate where the device isolation layer11 is formed. Generally, the stack insulating layer 18 includes first,second, and third insulating layers 12, 14, and 16 which areconventionally made of thin thermal oxide, silicon nitride, and CVDoxide, respectively.

[0007] Referring now to FIG. 3, the gate conductive layer 20 and thestack insulating layer 18 are sequentially patterned to form a pluralityof gate electrodes 30 crossing the device isolation layer 11. A tunneloxide layer 22, a charge storage layer 24, and a blocking insulatinglayer 26 are sequentially stacked between the gate electrode 30 and theactive region 13. In case sidewalls of the tunnel oxide layer 22, thecharge storage layer 24, and the blocking insulating layer 26 aredamaged by an etch, a defect density increases with increased trapdensity around edges of the tunnel oxide layer 22 and the blockinginsulating layer 26. As a result, it is likely to generate atrap-assisted leakage current to the gate electrode 30 and thesemiconductor substrate 10 through the high-density trap.

[0008] Referring now to FIG. 4, a thermal oxidation process is carriedout for the semiconductor substrate in order to alleviate the damage ofthe sidewalls of the blocking insulating layer 26 and the gate electrode30. As a result, a capping insulating layer 32 is formed on a sidewalland a top surface of the gate electrode 30.

[0009] Referring now to FIG. 5, using the gate electrode 30 and thecapping insulating layer 32 as an ion implanting mask, impurities areimplanted into the semiconductor substrate to form an impurity diffusionlayer 34. A sidewall spacer 36 is then formed on sidewalls of the chargestorage layer 24, the blocking insulating layer 26, and the cappinginsulating layer 32 that are sequentially stacked. As illustrated inFIG. 4 and FIG. 5, oxygen atoms are diffused through an interfacebetween the semiconductor substrate 10 and the tunnel oxide layer 22during the thermal oxidation process. At this time, an edge of thetunnel oxide layer 22 becomes thick (i.e., a bird's beak phenomenonoccurs) because it is oxidized by the diffused oxygen atoms. This leadsto a drop in device operational speed. Furthermore, a trap densitybecomes high at the relatively thicker edge of the tunneling oxide layer22 thereby increasing trap-assisted leakage current through the edge. Asthe bird's beak phenomenon causes a thickness variation of a tunneloxide layer to be high in a cell array, device characteristics becomenon-uniform. The more a gate line width decreases, the more thethickness of the tunnel oxide layer 22 increases. Therefore, what isneeded is a non-volatile memory device with a structure to overcomedevice operational characteristic defects that result from a tunneloxide layer of high trap density and from bird's beak phenomenon.

SUMMARY OF THE INVENTION

[0010] A feature of the present invention is to provide a non-volatilememory device having a conformal tunnel oxide layer without a bird'sbeak phenomenon, and to provide a method of fabricating the same.

[0011] Another feature of the present invention is to provide anon-volatile memory device that can minimize the influence oftrap-assisted tunneling, and to provide a method of fabricating thesame.

[0012] According to an aspect of the present invention, a non-volatilememory device includes a charge storage layer and a gate electrode. Thegate electrode crosses an active region between device isolation layersformed in a semiconductor substrate. The charge storage layer intervenesbetween the gate electrode and the active region. An edge of the chargestorage layer extends to form a protruding part that protrudes from asidewall of the gate electrode.

[0013] In a preferred embodiment of the present invention, the chargestorage layer is isolated by the device isolation layer or is successiveunder the gate electrode. A blocking insulating layer intervenes betweenthe gate electrode and the charge storage layer, and a tunnel oxidelayer intervenes between the charge storage layer and the active region.The non-volatile memory device further includes a first sidewall spaceron both sidewalls of the gate electrode. The width of the charge storagelayer is preferably approximately equal to the sum of a width of thegate electrode and widths of the first sidewall spacers. Further, thenonvolatile memory device may include a second sidewall spacer thatcovers a sidewall of the charge storage layer and the first sidewallspacer. A gate capping insulating layer may intervene between thesidewall of the gate electrode and the sidewall spacer.

[0014] The non-volatile memory device has a cell array region and aperipheral circuit region. A first transistor including a wordline and astack insulating layer is formed on an active region. The stackinsulating layer comprises a tunnel oxide layer, a charge storage layer,and a blocking insulating layer and a first transistor. A secondtransistor including at least a gate insulating layer and a gateelectrode is formed in the peripheral region. The first sidewall spacermay be formed on each sidewall of the gate electrodes in the first andsecond transistors. Further, a second sidewall spacer may be formed onthe first sidewall spacer that is formed on each sidewall of thewordline and the gate electrode.

[0015] According to another aspect of the present invention, a method offabricating a nonvolatile memory device is provided. A stack insulatinglayer is formed on an active region of a semiconductor substrate. Thestack insulating layer comprises at least first, second, and thirdinsulating layers that are sequentially stacked. A plurality of gateelectrodes crossing the active region are formed on a semiconductorsubstrate including the stack insulating layer. The stack insulatinglayer is patterned to form a tunnel oxide layer, a charge storage layer,and a blocking insulating layer that are sequentially stacked betweenthe gate electrode and the active region. The tunneling oxide layer, thecharge storage layer, and the blocking insulating layer correspond tothe first, second, and third insulating layers, respectively. An edge ofthe charge storage layer has a protruding part that protrudes from asidewall of the gate electrode.

[0016] Specifically, the device isolation layer may be formed using aconventional trench isolation technology. In this case, the stackinsulating layer is formed on an overall surface of a semiconductorsubstrate where the device isolation layer is formed. A gate conductivelayer is formed on the stack insulating layer, and then is patterned toform a gate electrode crossing the active region. Alternatively, thedevice isolation layer may be formed using a self-aligned trenchisolation technology. In this case, a stack insulating layer and a lowergate conductive layer are sequentially formed on an active regionbetween the device isolation layers. An upper gate conductive layer isformed on an overall surface of a semiconductor substrate where thedevice isolation layer is formed. Thereafter, the upper and lower gateconductive layers are sequentially patterned to form the active regioncrossing the active region.

[0017] In a preferred embodiment of the present invention, a firstsidewall spacer is formed on a sidewall of the gate electrode so as toform the protruding part of the charge storage layer. Using the firstsidewall spacer and the gate electrode as an etch mask, at least thethird and second insulating layers are etched to form a blockinginsulating layer protruding from the sidewall of the gate electrode anda charge storage layer. Alternatively, prior to formation of the firstsidewall spacer, the third insulating layer exposed to both sides of thegate electrode may be removed. In this case, the charge storage layerhas a protruding part that protrudes from the sidewall of the gateelectrode, and the first sidewall spacer covers the sidewall of the gateelectrode and an upper portion of the protruding part. Further, a secondsidewall spacer may be formed to cover sidewalls of the charge storagelayer and the first sidewall spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a top plan view of a conventional non-volatile memorydevice.

[0019]FIG. 2 through FIG. 5 are cross-sectional flow diagrams showingthe steps of fabricating the conventional non-volatile memory device,taken along a line I-I′ of FIG. 1.

[0020]FIG. 6 is a top plan view of a non-volatile memory deviceaccording to first and second embodiments of the present invention.

[0021]FIG. 7 is a cross-sectional view of the non-volatile memory deviceaccording to the first embodiment, taken along a line II-II′ of FIG. 6.

[0022]FIG. 8 through FIG. 11 are cross-sectional flow diagrams showingthe steps of fabricating the non-volatile memory device according to thefirst embodiment, taken along the line II-II′ of FIG. 6.

[0023]FIG. 12 through FIG. 14 are cross-sectional flow diagrams showingthe steps of fabricating the non-volatile memory device according to thesecond embodiment, taken along the line II-II′ of FIG. 6.

[0024]FIG. 15 is a top plan view of a non-volatile memory deviceaccording to third and fourth embodiments of the present invention.

[0025]FIG. 16 is a cross-sectional view of a non-volatile memory deviceaccording to the third embodiment, taken along a line III-III′ of FIG.15.

[0026]FIG. 17 through FIG. 19 are cross-sectional flow diagrams showingthe steps of fabricating the non-volatile memory device according to thethird embodiment, taken along the line III-III′ of FIG. 15.

[0027]FIG. 20 is a cross-sectional view of a structure according to thefourth embodiment, taken along the line III-III′ of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The present invention will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. The invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. In the drawings, the thickness of layers and regions areexaggerated for clarity. It will also be understood that when a layer isreferred to as being “on” another layer or substrate, it can be directlyon the other layer or substrate, or intervening layers may also bepresent. Like numbers refer to like elements throughout.

[0029]FIG. 6 is a top plan view illustrating a non-volatile memorydevice according to first and second embodiments of the presentinvention, in which a region “a” is a cell array region and a region “b”is a peripheral circuit region. FIG. 7 is a cross-sectional viewillustrating the non-volatile memory device according to the firstembodiment, taken along a line II-II′ of FIG. 6.

[0030] Referring now to FIG. 6 and FIG. 7, a device isolation layer 101is formed in a predetermined region of a semiconductor substrate 100.The device isolation layer 101 defines a plurality of first activeregions 103 in the cell array region “a”, and a second active region 203in the peripheral circuit region “b”. A plurality of wordlines 140crossing over the first active regions 103 and the device isolationlayer 101 are formed in the cell array region “a”. A stack insulatinglayer intervenes between the wordlines 140 and the first active regions103, and includes a tunnel oxide layer 152, a charge storage layer 154,and a blocking insulating layer 156 that are sequentially stacked. It ispreferable that the tunnel oxide layer 154, the charge storage layer154, and the blocking insulating layer 156 are made of thermal oxide,silicon nitride, and CVD oxide, respectively. Also, the blockinginsulating layer 156 and the charge storage layer 154 overlap with thewordline 140 to cross over the first active region 103 and the deviceisolation layer 101. A sidewall of the wordline 140 is covered with afirst sidewall spacer.

[0031] Furthermore, a gate capping oxide layer 142 may intervene betweenthe wordline 140 and the first sidewall spacer 146. A width of thecharge storage layer 154 is larger than that of the wordline 140 atleast, so that the blocking insulating layer 156 has a protruding part151 protruding from a sidewall of the wordline 140. Therefore, althougha high electric field is applied between the wordline 140 and the firstactive regions 103 by a program voltage or an erase voltage, an electricfield applied to the protruding part 151 is relatively weak. This causesa conspicuous decrease in a leakage current flowing through a blockinginsulating layer 156 and a tunnel oxide layer 152 that are located overand under the protruding part 151, respectively. As a result, a softprogram characteristic or a data retention characteristic can beimproved.

[0032] The first sidewall spacer 146 covers not only the sidewall of thewordline 140 but also a top of the protruding part 151 . The secondsidewall spacer 146 may cover an outer sidewall of the first sidewallspacer 148 and a sidewall of the charge storage layer 154. A firstimpurity diffusion layer 150 is formed in the first active region 103between the wordlines 140. Therefore, a first cell transistor is formedat an intersection of the wordline 140 and the first active region 103.In this case, the tunnel oxide layer 152 under the wordline 140 has auniform thickness. That is, a thick tunnel oxide layer caused by abird's beak phenomenon is not formed at least under an edge of thewordline 140. Thus, a plurality of first transistors in the cell arrayregion “a” have the equivalent threshold voltage.

[0033] A gate electrode 240 crossing over the second active region 203is formed in the peripheral circuit region “b”. The first sidewallspacer 146 covers the gate insulating layer 202 between the gateelectrode 240 and the second active region 203, and a sidewall of thegate electrode 240. The second sidewall spacer may cover an outersidewall of the first sidewall spacer 146. A gate capping layer 142 mayintervene between the fist sidewall spacer 142 and the gate electrode240. A dual-structured impurity diffusion layer 254 is formed in thesecond active region 203 at both sides of the gate electrode 240. Thedual-structured impurity diffusion layer 254 includes a second impuritydiffusion layer 250 and a third impurity diffusion layer 252 thatcorrespond to a lightly doped impurity diffusion layer and a heavilydoped impurity diffusion layer, respectively.

[0034]FIG. 8 through FIG. 11 are cross-sectional flow diagrams showingthe steps of fabricating a non-volatile memory device according to afirst embodiment of the present invention, taken along a line II-II′ ofFIG. 6.

[0035] Referring now to FIG. 8, a device isolation layer 101 is formedin a semiconductor substrate 100 to define a first active region 103 anda second active region 203 in a cell array region “a” and a peripheralcircuit region “b”, respectively. A stacking insulating layer 108 and agate conductive layer 120 are sequentially formed in a cell array region“a” of a semiconductor substrate 100 where the device isolation layer101 is formed. At the same time, a gate insulating layer 108 and a gateconductive layer 120 are sequentially formed in a peripheral region “b”of the semiconductor substrate where the device isolation layer 101 isformed. Preferably, the stack insulating layer 108 is formed bysequentially stacking first, second, and third insulating layers 102,104, and 106. Preferably, the first insulating layer 102 is made ofthermal oxide. Preferably, the first insulating layer has a thickness ofapproximately 15 Å-35 Å in order to lower a program and erase voltages.In this embodiment, it is preferable that the second insulating layer104 has a thickness of approximately 40 Å-100 Å, and the thirdinsulating layer 106 has a thickness of approximately 40 Å-120 Å. Thegate conductive layer 120 may be made of polysilicon, or polycide thatis formed by sequentially stacking polysilicon and metal silicide.

[0036] Referring now to FIG. 9, the gate conductive layer 120 ispatterned to form a plurality of wordlines 140 crossing the first activeregions 103 in the cell array region “a”, and to form a gate electrode240 at least on the second active region 203 in the peripheral circuitregion “b”. The third insulating layer 106 exposed between the wordlines140 is overetched or attacked by plasma while etching the gateconductive layer 120. Therefore, a defect site may be created in thethird insulating layer around an edge of the wordline 140. Subsequently,a trap-to-trap tunneling may occur through the defect site. Chargesstored in a later-formed charge storage layer are then discharged to agate electrode, having an undesirable influence on device operations.Preferably, in order to overcome the above disadvantages, a thermaloxidation process is performed for a semiconductor substrate where thewordline 140 and the gate electrode 240 are formed. Thus, the damage ofthe third insulating layer 106 can be alleviated. As a result, a gatecapping oxide layer 142 is formed on sidewalls and top surfaces of thewordline 140 and the gate electrode 240.

[0037] Referring now to FIG. 10, impurities are implanted into the firstactive region 103 between the wordlines 140 to form a first impuritydiffusion layer 150. Also, impurities are implanted into the secondactive region 203 at both sides of the gate electrode 240 to form asecond impurity diffusion layer 250. Alternatively, the first and secondimpurity diffusion layers 150 and 250 may be formed at the same time orprior to formation of the gate capping oxide layer 142. Thereafter, aspacer insulating layer 144 is conformally formed on an entire surfaceof the resultant structure in which the first and second impuritydiffusion layers 150 and 250 are formed. Preferably, the spacerinsulating layer 144 is made of silicon nitride or oxide.

[0038] Referring now to FIG. 11, the spacer insulating layer 144 isanisotropically etched to form a first sidewall spacer 146 on sidewallsof the wordline 140 and the gate electrode 240. If the spacer insulatinglayer 144 is made of oxide, the third insulating layer 106 is alsoetched during the anisotropic etch to expose the second insulating layer104. If the spacer insulating layer 144 is made of silicon nitride, thethird insulating layer 106 is etched using the wordline 140 and thefirst sidewall spacer 146 as an etch mask following formation of thefirst sidewall spacer 146.

[0039] Using the first sidewall spacer 146 and the gate electrode 140 asan etch mask, at least the second insulating layer 108 is then etched toform at least second and third insulating layer patterns 154 and 156between the wordline 140 and the first active region 103. Edges of thesecond and the third insulating layer patterns 154 and 156 are extendedto form a protruding part 151 that protrudes from both sides of thewordline 140. The second insulating layer patterns 154 correspond to acharge storage layer, and the third insulating layer pattern 156intervened between the wordline 140 and the second insulating layer 154corresponds to a blocking insulating layer. The first insulating layer152 under the wordline 140 corresponds to a tunnel oxide layer.

[0040] Following formation of the first sidewall spacer 146, impuritiesare implanted into the second active region exposed to both sides of thegate electrode 240 in the peripheral circuit region “b” to form a thirdimpurity diffusion layer 252. Subsequently, a dual-structured impuritydiffusion layer 254 is formed in the second active region at both sidesof the gate electrode 240. The third impurity diffusion layer 252 may beformed before or after formation of the second insulating layer pattern154.

[0041] Following formation of the third and the second insulating layerpatterns 156 and 154, a second sidewall spacer 148 (see FIG. 7) mayfurther be formed in the cell array region “a” and the peripheralcircuit region “b”. In the cell array region “b”, the second sidewallspacer 148 covers sidewalls of the first sidewall spacer 146, the thirdinsulating layer pattern 156, and the second insulating layer pattern154. In the peripheral circuit region “b”, the second sidewall spacer148 covers the first sidewall spacer 146. If the second sidewall spacer148 is further formed, the third impurity diffusion layer 252 may beformed in the second active region 203 exposed to both sides of the gateelectrode 240 following formation of the second sidewall spacer 148.Alternatively, the first and second impurity diffusion layers 150 and250 may be formed following the formation of the first sidewall spacer146, and the third impurity diffusion layer 252 may be formed followingthe formation of the second sidewall spacer 148.

[0042] As a result, a width of the charge storage layer 158 is equal tothe sum of the width of the gate electrode 140 and the widths of thesidewall spacers 146. In other words, the nonvolatile memory device ofthe invention has a protruding part that is formed by extending an edgeof the charge storage layer 158 to protrude from a sidewall of the gateelectrode 140. Therefore, even if defect sites are created in insulatinglayers over/under the protruding part, device operation characteristicsare scarcely influenced by the defect sites compared with a prior art.Because an edge of the tunnel oxide layer 152 also protrudes from thegate electrode 140 wherein a bird's beak phenomenon may occur insubsequent annealing processes, the non-volatile memory device of theinvention has an excellent data retention characteristic compared withthe prior art.

[0043]FIG. 12 through FIG. 14 are cross-sectional flow diagrams forexplaining the steps of fabricating a non-volatile memory deviceaccording to a second embodiment of the present invention.

[0044] Referring now to FIG. 12, steps until formation of a gateconductive layer 120 (see FIG. 8) in the second embodiment are identicalto those in the first embodiment, as described in FIG. 8. The gateconductive layer 120 and the third insulating layer 106 (see FIG. 8) aresequentially patterned to form a wordline 140 and a third insulatinglayer pattern 156 a on the second insulating layer 104 in the cell arrayregion “a” and to form a gate electrode 240 in the peripheral circuitregion “b”. The third insulating layer pattern 156 corresponds to ablocking insulating layer. Furthermore, a thermal oxidation process iscarried out for the semiconductor substrate to form a gate capping oxidelayer 142′ on a sidewall and a top surface of the wordline 140 and thegate electrode 240.

[0045] Referring now to FIG. 13, in the cell array region “a”,impurities are implanted into a first active region 103 between thewordlines 140 to form a first impurity diffusion layer 150. In theperipheral circuit region “b”, impurities are implanted into a secondactive region 203 exposed to both sides of the gate electrode 240 toform a second impurity diffusion layer 250. A spacer insulating layer144 is conformally formed on an entire surface of a semiconductorsubstrate 100 where the wordline 140 and gate electrode 240 are formed.The spacer insulating layer 144 is made of silicon nitride or oxide.

[0046] Referring now to FIG. 14, the spacer insulating layer 144 isanisotropically etched to form a first sidewall spacer 146 on sidewallsof the wordline 140 and the gate electrode 240. If the spacer insulatinglayer 144 is made of silicon nitride, the second insulating layer 104 isalso etched to form the first sidewall spacer 146 and a secondinsulating layer pattern 154 with a protruding part 151 a protrudingfrom the sidewall of the wordline 140 while anisotropically etching thespacer insulating layer 144.

[0047] If the spacer insulating layer 144 is made of oxide, it isanisotropically etched to form a first sidewall spacer 146 on thesidewall of the wordline 140. Using the first sidewall spacer 146 andthe gate electrode 140 as an etch mask, the second insulating layer 104is then etched to form a second insulating layer pattern 154 with aprotruding part 151 a protruding from the sidewall of the gate electrode140. The second insulating layer pattern 154 corresponds to a chargestorage layer. Following formation of the first sidewall spacer 146,impurities are implanted into the second active region 203 at both sidesof the gate electrode 240 to form a third impurity diffusion layer 252.As a result, a dual-structured impurity diffusion layer 254 is formed inthe second active region 203 at both sides of the gate electrode 240.The third impurity diffusion layer 252 may be formed after or beforeformation of the second insulating layer pattern 154.

[0048] Following formation of the second insulating layer pattern 154, asecond sidewall spacer 148 (see FIG. 7) may further be formed in thecell array region “a” and the peripheral circuit region “b”. In the cellarray region “a”, the second sidewall spacer 148 of FIG. 7 covers thefirst sidewall spacer 146 and the sidewalls of the third and secondinsulating layer pattern 156 a and 154. In the peripheral circuit region“b”, the second sidewall spacer 148 of FIG. 7 covers the first sidewallspacer 146. In this case, the third impurity diffusion layer 252 may beformed in the second active region 203 at both sides of the gateelectrode 240 following formation of the second sidewall spacer 148.Alternatively, the first and second impurity diffusion layers 150 and250 may be formed following formation of the first sidewall spacer 146,and the third impurity diffusion layer 252 may be formed following theformation of the second sidewall spacer 148.

[0049] As illustrated in the drawings, constructions of the non-volatilememory devices according to the first and second embodiments are verysimilar to each other. A difference therebetween is that the thirdinsulating layer pattern 156 a is self-aligned to the wordline 140, andthus a width of the third insulating layer pattern 156 a is identical toa width of the wordline 140. Therefore, the first sidewall spacer 146covers a sidewall of the gate electrode 140, a sidewall of the thirdinsulating layer 156 a, and a top surface of the protruding part 151 a.

[0050]FIG. 15 is a top plan view illustrating a non-volatile memorydevice according to third and fourth embodiments of the presentinvention, in which reference numerals “a” and “b” denote a cell arrayregion and a peripheral circuit region, respectively. FIG. 16 is across-sectional view illustrating a non-volatile memory device accordingto a third embodiment of the present invention, taken along a lineIII-III′ of FIG. 15.

[0051] Referring now to FIG. 15 and FIG. 16, a device isolation layer101′ is formed in a predetermined area of a semiconductor substrate 100to define a plurality of first active regions 103′ in the cell arrayregion “a”, and to define a second active region 203′ in the peripheralcircuit region “b”. A plurality of wordlines 183 crossing over the firstactive regions 103′ and the device isolation layer 101′ are formed inthe cell array region “a”. A stack insulating layer intervenes betweenthe wordlines 183 and the first active regions 103′, and includes atunnel oxide layer 162, a charge storage layer 194, and a blockinginsulating layer 196 that are sequentially stacked. It is preferablethat the tunnel oxide layer 162, the charge storage layer 194, and theblocking insulating layer 196 are made of thermal oxide, siliconnitride, and CVD oxide, respectively. A sidewall of the wordline 183 iscovered with a first sidewall spacer 186.

[0052] Furthermore, a gate capping oxide layer 182 may intervene betweenthe wordline 183 and the first sidewall spacer 186. Since the chargestorage layer 194 and the blocking insulating layer 196 have largerwidths than the wordline 183, they have a protruding part 191 thatprotrudes from the sidewall of the wordline 183. Therefore, although ahigh electric field is applied between the wordline 183 and the firstactive region 103′ by a program voltage or an erase voltage, an electricfield applied to the protruding part 191 is weak. As a result, a leakagecurrent flowing through the blocking insulating layer 196 and the tunneloxide layer 162 each being formed over and under the protruding part 191is considerably reduced to improve a soft program characteristic or adata retention characteristic.

[0053] The first sidewall spacer 186 covers not only the sidewall of thewordline 183 but also a top surface of the protruding part 191.Furthermore, a second sidewall spacer 188 (see FIG. 19) may cover anouter sidewall of the first sidewall spacer 186, a sidewall of theblocking insulating layer 196, and a sidewall of the charge storagelayer. A first impurity diffusion layer 190 is formed in the firstactive region 103′ between the wordlines 183. Therefore, a first celltransistor is formed at an intersection of the wordline 183 and thefirst active region 103′. In this case, the tunnel oxide layer 152 underthe wordline 140 has a uniform thickness. That is, a thick tunnel oxidelayer caused by a bird's beak phenomenon is not formed at least under anedge of the wordline 183. Thus, a plurality of first transistors in thecell array region “a” have the equivalent threshold voltage.

[0054] In the peripheral circuit region “b”, a gate electrode 283 isformed to cross over the second active region 203. A gate insulatinglayer 262 intervenes between the gate electrode 283 and the secondactive region 203. A sidewall of the gate electrode 283 is covered withthe first sidewall spacer 186. Furthermore, an outer sidewall of thefirst sidewall spacer 186 may be covered with a second sidewall spacer,as described above. The gate capping oxide layer 182 may intervenebetween the first sidewall spacer 186 and the gate electrode 283.Dual-structured impurity diffusion layers 294 are formed in the secondactive region 203′ at both sides of the gate electrode 283. Thedual-structure impurity diffusion layer 294 includes second and thirdimpurity diffusion layers 290 and 292. As a result, the impuritydiffusion layer 294 corresponds to an LDD-type source/drain region, andthe second impurity diffusion layer 290 and the third impurity diffusionlayer 292 correspond to a lightly doped diffusion layer and a heavilydoped impurity diffusion layers, respectively.

[0055] A difference between the first and third embodiments is that thedevice isolation layer 101′ is formed using a self-aligned shallowtrench technology (S. A. STI). Accordingly, the wordline 183 includes anupper wordline 180 crossing the first active region 103′ and a lowerwordline 181 intervened between the upper wordline 180 and the firstactive region 103′. As shown in FIG. 16, the gate electrode 283 mayinclude a lower gate electrode 281 and an upper gate electrode 280.

[0056]FIG. 17 through FIG. 19 are cross-sectional flow diagrams forexplaining the steps of fabricating the non-volatile memory deviceaccording to the third embodiment of the present invention, taken alonga line III-III′ of FIG. 15.

[0057] Referring now to FIG. 17, a stack insulating layer 168 is formedon a semiconductor substrate 100. After the stack insulating layer 168formed in a peripheral circuit region “b” is removed and a gateinsulating layer 262 is formed, a lower gate conductive layer 169 and ahard mask layer are formed on an entire surface of the substrate 100.The hard mask layer, the lower gate conductive layer 169, the stackinsulating layer 168, and the substrate 100 in a cell array region “a”and the hard mask layer, the lower gate electrode 169, and the substrate100 are sequentially patterned to form a trench in a predetermined areaof the substrate 100. Preferably, the first insulating layer 162 isformed to a thickness of 15 Å-35 Å in order to make a tunneling ofcharges even in low program and erase voltages. As above-mentioned inthe first embodiment, the second insulating layer 164 is preferably madeof silicon nitride to a thickness of 40 Å-100 Å, and the thirdinsulating layer 166 is preferably made of CVD oxide to a thickness of40 Å-120 Å. Thereafter, the trench area is filled with an insulatinglayer to form a device isolation layer 101′, and the hard mask layer isremoved.

[0058] Referring now to FIG. 18, the upper gate conductive layer 170 isformed on an entire surface of a semiconductor substrate 100 where thedevice isolation layer 101′ is formed. The upper gate conductive layer170 is preferably made of polysilicon, or polycide that is formed bysequentially stacking polysilicon and metal silicide.

[0059] Referring now to FIG. 19, the upper gate conductive layer 170 andthe lower gate conductive layer 169 are sequentially patterned to form aplurality of wordlines 183 crossing the first active region 103′ in thecell array region “a”, and to form a gate electrode 283 crossing thesecond active region 203′ in the peripheral circuit region “b”. In thesame manner as the first embodiment, a first impurity diffusion layer190 is formed in the first active region 103′ between the wordlines 183,and a second impurity diffusion layer 290 is formed in the second activeregion 203′ at both sides of the gate electrode 283. A first sidewallspacer 186 is formed on sidewalls of a wordline 183 and a gate electrode283. The wordline 183 includes lower and upper wordlines 181 and 180that are sequentially stacked, and the gate electrode 283 includes lowerand upper gate electrodes 281 and 280. Using the sidewall spacer 186 andthe gate electrode 183 in the cell array region “a” as an etch mask, atleast the third and second insulating layers 166 and 164 are etched toform third and second insulating layer patterns 196 and 194 between thegate electrode 183 and each of the active regions 103′.

[0060] An edge of the second insulating layer pattern 194 is extended tohave a protruding part 191 that protrudes from a sidewall of the gateelectrode 183. The second insulating layer pattern 194 corresponds to acharge storage layer, and the third insulating layer pattern 196intervened between the wordline 183 and the second insulating layerpattern 194 corresponds to a blocking insulating layer. The firstinsulating layer 162 intervened between the second insulating layerpattern 194 and the first active region 103′ corresponds to a tunneloxide layer. Following formation of the first sidewall spacer 186,impurities are implanted into the second active region 203′ at bothsides of the gate electrode 283 in the peripheral circuit region “b” toform a third impurity diffusion layer 292. Thus, a dual-structuredimpurity diffusion layer 294 is formed in the second active region 203′on either side (both sides) of the gate electrode 283. The thirdimpurity diffusion layer 292 may be formed before or after formation ofthe second insulating layer pattern 194.

[0061] Furthermore, a second sidewall spacer 188 may be formed in thecell array region “a” and the peripheral circuit region “b”. The secondsidewall spacer 188 covers not only sidewalls of the third and secondinsulating layer patterns 196 and 194 in the cell array region “a” butalso the first sidewall spacer 186 in the peripheral circuit region “b”.In this case, the first and second impurity diffusion layers 190 and 290may be formed following formation of the first sidewall spacer 186.Also, the third impurity diffusion layer 292 may be formed in the secondactive region 203′ on either side (both sides) of the gate electrode 283following formation of the second sidewall spacer 148.

[0062]FIG. 20 is a cross-sectional view illustrating a non-volatilememory device according to a modified version of the second embodiment,taken along a line III-III′ of FIG. 15.

[0063] Referring now to FIG. 20, in a fourth embodiment of theinvention, a device isolation layer is formed using a self-aligned shalltrench technology (S. A. STI), like the third embodiment. Steps untilformation of the gate conductive layer are identical to those in theforegoing modified version of the first embodiment. Subsequent steps areperformed in the same manner as the second embodiment, forming awordline 183 crossing a first active region 103′ in a cell array region“a” of a semiconductor substrate 100 and a gate electrode 283 extendedto an upper part of the device isolation layer 101′ in the second activeregion 203′ in the peripheral circuit region “b”. A gate capping oxidelayer 182′ may further be formed on sidewalls and top surfaces ofwordline 183 and gate electrode 283. A tunnel oxide layer 162, a chargestorage layer 194, and a blocking insulating layer 196 a aresequentially stacked on the first active region 103′ between deviceisolation layers 101 a, and are intervened between the wordline 183 andthe first active region 103′. The blocking insulating layer 196 a isself-aligned to the wordline 183, so that their widths are identical toeach other.

[0064] A sidewall of the charge storage layer 194 has a protruding part191 a that protrudes from a sidewall of the gate electrode. A firstsidewall spacer 186 is formed on the sidewall of the wordline 183 andthe protruding part 191 a of the charge storage layer 194 in the cellarray region “a”, and on the sidewall of the gate electrode 283 in theperipheral circuit region “b”. Furthermore, the second spacer 188 may beformed to cover the first sidewall spacer 186 and a sidewall of thecharge storage layer 194 in the cell array region “a”, and the firstsidewall spacer 186 in the peripheral circuit region “b”. A firstimpurity diffusion layer 190 is formed in the first active region 103′between the wordlines 183, and a dual-structured impurity diffusionlayer 294 is formed in a second active region 203′ on either side (bothsides) of the gate electrode 283. The dual-structured impurity diffusionlayer 294 includes second and third impurity diffusion layers 290 and292.

[0065] According to the present invention, an edge of a charge storagelayer is extended to have a protruding part that protrudes from asidewall of a gate electrode. With a high defect density, edges of ablocking insulating layer and a tunnel oxide layer also protrude fromthe sidewall of the gate electrode, which results in a conspicuousdecrease in a leakage current flowing through defect sites in the edgesof the blocking insulating layer and the tunnel oxide layer. Thus, adata retention characteristic can be improved in comparison with theprior art.

[0066] Furthermore, the invention makes it possible to lessendeterioration of repeated operation cycle characteristics, and to form atunnel oxide layer without a bird's beak under the gate electrode. Thus,the threshold voltage distribution range of memory cells can be reduced.

[0067] Those skilled in the art will readily implement the stepsnecessary to provide the structures and the methods disclosed herein,and will understand that the process parameters, materials, dimensions,and sequence of steps are given by way of example only and can be variedto achieve the desired structure as well as modifications that arewithin the scope of the invention. Variations and modifications of theembodiments disclosed herein may be made based on the description setforth herein, without departing from the spirit and scope of theinvention as set forth in the following claims.

What is claimed is:
 1. A non-volatile memory device comprising: an active region defined in a predetermined area of a semiconductor substrate; a gate electrode crossing over the active region; and a tunnel oxide layer, a charge storage layer, and a blocking insulating layer which are sequentially stacked between the gate electrode and at least the active region, wherein the charge storage layer has a protruding part which protrudes from a sidewall of the gate electrode.
 2. The non-volatile memory device of claim 1, wherein the tunnel oxide layer and the blocking insulating layer are made of silicon oxide, and the charge storage layer is made of silicon nitride.
 3. The non-volatile memory device of claim 1, wherein the blocking insulating layer is self-aligned to the gate electrode to have the same width as a width of the gate electrode.
 4. The non-volatile memory device of claim 3, further comprising a first sidewall spacer which covers the sidewall of the gate electrode and a sidewall of the blocking insulating layer, and is positioned on the protruding part of the charge storage layer.
 5. The non-volatile memory device of claim 4, wherein a width of the charge storage layer is equal to the sum of the width of the gate electrode and widths of the first sidewall spacers covering both sidewalls of the gate electrode.
 6. The non-volatile memory device of claim 4, further comprising a gate capping oxide layer intervened between the first sidewall spacer and the gate electrode.
 7. The non-volatile memory device of claim 4, further comprising a second sidewall spacer which covers an outer sidewall of the first sidewall spacer and a sidewall of the charge storage layer.
 8. The non-volatile memory device of claim 1, wherein the blocking insulating layer has a protruding part which protrudes from the sidewall of the gate electrode, and has the same width as the width of the charge storage layer.
 9. The non-volatile memory device of claim 8, further comprising a first sidewall spacer which covers the sidewall of the gate electrode, and is positioned on the protruding part of the blocking insulating layer.
 10. The non-volatile memory device of claim 9, wherein the width of the charge storage layer is equal to the sum of the width of the gate electrode and widths of the first sidewall spacers covering the both sidewalls of the gate electrode.
 11. The non-volatile memory device of claim 9, further comprising a gate capping oxide layer intervened between the gate electrode and the first sidewall spacer.
 12. The non-volatile memory device of claim 9, further comprising a second sidewall spacer covering an outer sidewall of the first sidewall spacer, the sidewall of the blocking insulating layer, and the sidewall of the charge storage layer.
 13. A non-volatile memory device comprising: a plurality of parallel device isolation layers formed in a predetermined area of a semiconductor substrate to define at least one active region; a gate electrode crossing the active region and the device isolation layers adjacent to both sides of the active region; and a tunnel oxide layer, a charge storage layer, and a blocking insulating layer which are sequentially stacked between the gate electrode and at least the active region, wherein the charge storage layer is extended in parallel with the device isolation layer to have a protruding part which protrudes from a sidewall of the gate electrode.
 14. The non-volatile memory device of claim 13, wherein the gate electrode includes: an upper gate electrode crossing the active region and the device isolation layer; and a lower gate electrode intervened between the upper gate electrode and the active region, wherein the tunnel oxide layer, the charge storage layer, the blocking insulating layer, and the lower gate electrode are sequentially stacked on the active region between the adjacent device isolation layers.
 15. The non-volatile memory device of claim 13, wherein the charge storage layer and the blocking insulating layer are extended in parallel with the gate electrode to cross cover the active region and the device isolation layers.
 16. The non-volatile memory device of claim 13, wherein the blocking insulating layer is self-aligned to the gate electrode to have the same width as a width of the gate electrode.
 17. The non-volatile memory device of claim 16, further comprising a first sidewall spacer which covers a sidewall of the gate electrode and a sidewall of the blocking insulating layer, and is located on the protruding part of the charge storage layer.
 18. The non-volatile memory device of claim 17, further comprising a capping oxide layer intervened between the first sidewall spacer and the gate electrode.
 19. The non-volatile memory device of claim 17, further comprising a second sidewall spacer covering an outer sidewall of the first sidewall spacer and a sidewall of the charge storage layer.
 20. The non-volatile memory device of claim 13, wherein the blocking insulating layer has a protruding part which protrudes from the sidewall of the gate electrode, and has the same width as a width of the charge storage layer.
 21. The non-volatile memory device of claim 20, further comprising a first sidewall spacer which covers the sidewall of the gate electrode, and is located on the protruding part of the blocking insulating layer.
 22. The non-volatile memory device of claim 21, further comprising a gate capping oxide layer intervened between the gate electrode and the first sidewall spacer.
 23. The non-volatile memory device of claim 21, further comprising a second sidewall spacer covering an outer sidewall of the first sidewall spacer, a sidewall of the blocking insulating layer, and a sidewall of the charge storage layer.
 24. A non-volatile memory device with a cell array region and a peripheral circuit region, comprising: device isolation layers formed in a predetermined area of a semiconductor substrate to define a first active region and a second active region in the cell array region and the peripheral circuit regions, respectively; a gate electrode crossing the second active region; a gate insulating layer intervened between the second active region and the gate electrode; a plurality of wordlines crossing the first active region; and a stack insulating layer intervened between the wordlines and at least the first active region, wherein the stack insulating layer includes a tunnel oxide layer, a charge storage layer, and a blocking insulating layer which are sequentially stacked; and wherein at least the charge storage layer is extended across the wordlines to have a protruding part at both sides of the wordlines.
 25. The non-volatile memory device of claim 24, wherein each of the wordlines includes: an upper wordline crossing over the first active region and the device isolation layers adjacent to both sides of the first active region; and a lower wordline intervened between the first active region and the upper wordline, wherein the stack insulating layer and the lower wordline are sequentially stacked on the first active region between the device isolation layers.
 26. The non-volatile memory device of claim 25, wherein gate electrode includes: an upper gate electrode crossing over the second active region and the device isolation layer adjacent thereto; and a lower gate electrode intervened between the upper gate electrode and the second active region, wherein the gate electrode and the lower gate electrode are sequentially stacked on the second active region.
 27. The non-volatile memory device of claim 24, wherein the charge storage layer and the blocking insulating layer are extended in parallel with the wordline to cross over the active region and the device isolation layers.
 28. The non-volatile memory device of claim 24, wherein the blocking insulating layer is self-aligned to the overlying wordline to have the same width as a width of the wordline.
 29. The non-volatile memory device of claim 28, further comprising a first sidewall spacer which covers a sidewall of the wordline and a sidewall of the blocking insulating layer, and is located on the protruding part of the charge storage layer.
 30. The non-volatile memory device of claim 29, further comprising a second sidewall spacer covering an outer sidewall of the first sidewall spacer and the sidewall of the charge storage layer.
 31. The non-volatile memory device of claim 24, wherein the blocking insulating layer has a protruding part which protrudes from the sidewall of the wordline, and has the same width as a width of the charge storage layer.
 32. The non-volatile memory device of claim 31, further comprising a first sidewall spacer which covers the sidewall of the wordline, and is located on the protruding part of the blocking insulating layer.
 33. The non-volatile memory device of claim 32, further comprising a second sidewall spacer covering an outer sidewall of the first sidewall spacer, a sidewall of the blocking insulating layer, and a sidewall of the charge storage layer.
 34. The non-volatile memory device of claim 24, further comprising a source/drain region which is formed in the second active region at both sides of the gate electrode, and has a LDD (lightly doped drain) structure.
 35. A method of fabricating a non-volatile memory device, comprising the steps of: forming a stack insulating layer on a semiconductor substrate by sequentially stacking first, second and third insulating layers; forming a gate electrode crossing over the stack insulating layer; and forming a charge storage layer and a blocking insulating layer which are sequentially stacked between the gate electrode and the first insulating layer by patterning the third and second insulating layers, wherein at least the second insulating layer is patterned so that the charge storage layer has a protruding part which protrudes from a sidewall of the gate electrode.
 36. The method of claim 35, wherein the first and third insulating layers are made of silicon oxide, and the second insulating layer is made of silicon nitride.
 37. The method of claim 35, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: etching the third insulating layer by using the gate electrode as an etch mask to form a blocking insulating layer which is self-aligned to the gate electrode; forming a first sidewall spacer on the sidewall of the gate electrode and a sidewall of the blocking insulating layer; and etching the second insulating layer by using the gate electrode and the first sidewall spacer as an etch mask to form a charge storage layer whose width is larger than a width of the gate electrode.
 38. The method of claim 37, further comprising a steps of forming a gate capping oxide layer at least on the sidewall of the gate electrode prior to formation of the first sidewall spacer.
 39. The method of claim 37, further comprising a step of forming a second sidewall spacer on an outer sidewall of the first sidewall spacer and the sidewall of the charge storage layer.
 40. The method of claim 35, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: forming a first sidewall spacer on the sidewall of the gate electrode; and sequentially etching third and second insulating layers by using the gate electrode and the first sidewall spacer to form a blocking insulating layer having a protruding part under the first sidewall spacer and a charge storage layer which is self-aligned to the blocking insulating layer.
 41. The method of claim 40, further comprising a step of forming a gate capping oxide layer at least on the sidewall of the gate electrode prior to formation of the first sidewall spacer.
 42. The method of claim 40, further comprising a step of forming a second sidewall spacer on the outer sidewall of the first sidewall spacer, the sidewall of the blocking insulating layer, and the sidewall of the charge storage layer.
 43. A method of fabricating a non-volatile memory device, comprising the steps of: forming a device isolation layer and a stack insulating layer, wherein the device isolation layer is formed in a predetermined area of a semiconductor substrate to define an active region, and the stack insulating layer includes first, second and third insulating layers which are sequentially stacked at least on the active region; forming a gate electrode crossing the active region on the stack insulating layer; and forming a charge storage layer and a blocking insulating layer which are sequentially stacked between the first insulating layer and the gate electrode by patterning the third to second insulating layers, wherein at least the second insulating layer is patterned so that the charge storage layer has a protruding part which protrudes from the sidewall of the gate electrode.
 44. The method of claim 43, wherein the first and third insulating layers are made of silicon oxide, and the second insulating layer is made of silicon nitride.
 45. The method of claim 43, wherein the step of forming the device isolation layer, the stack insulating layer, and the gate electrode includes the steps of: sequentially forming a first insulating layer, a second insulating layer, a third insulating layer, and a lower gate conductive layer on an entire surface of the substrate; sequentially patterning the lower gate conductive layer, the third insulating layer, the second insulating layer, and the first insulating layer to form a trench region which defines an active region in a predetermined area of the substrate; forming a device isolation layer to fill the trench area; forming a lower gate conductive layer on an entire surface of a resultant structure including the device isolation layer; and sequentially patterning the upper gate conductive layer and the patterned lower gate conductive layer to form a lower gate electrode intervened between the gate electrode and the active region as well as an upper gate electrode crossing over the active region and the device isolation layer.
 46. The method of claim 43, wherein the step of forming the device isolation layer, the stack insulating layer, and the gate electrode includes the steps of: forming a device isolation layer to define an active region in a predetermined area of the substrate; sequentially forming first to third insulating layers and a gate conductive layer on an entire surface of a resultant structure including the device isolation layer; and patterning the gate conductive layer.
 47. The method of claim 43, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: etching the third insulating layer by using the gate electrode as an etch mask to form a blocking insulating layer which is self-aligned to the gate electrode; forming a first sidewall spacer on the sidewall of the gate electrode and the sidewall of the blocking insulating layer; and etching the second insulating layer by using the gate electrode and the first sidewall spacer as an etch mask to form a charge storage layer whose width is larger than a width of the gate electrode.
 48. The method of claim 47, further comprising a step of forming a gate capping oxide layer at least on the sidewall of the gate electrode prior to formation of the first sidewall spacer.
 49. The method of claim 49, further comprising a step of forming a second sidewall spacer on the outer sidewall of the first sidewall spacer and the sidewall of the charge storage layer.
 50. The method of claim 43, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: forming a first sidewall spacer on the sidewall of the gate electrode; and sequentially etching the third and second insulating layers by using the gate electrode and the first sidewall spacer as an etch mask to form a blocking insulating layer having a protruding part under the first sidewall spacer and a charge storage layer which is self-aligned to the blocking insulating layer.
 51. The method of claim 50, further comprising a step of forming a gate capping oxide layer at least on the sidewall of the gate electrode prior to formation of the first sidewall spacer.
 52. The method of claim 50, further comprising a step of forming a second sidewall spacer on the outer sidewall of the first sidewall spacer, the sidewall of the blocking insulating layer, and the sidewall of the charge storage layer.
 53. A method of fabricating a non-volatile memory device with a cell array region and a peripheral circuit region, comprising the steps of: forming not only a device isolation layer in a predetermined area of a semiconductor substrate to define a first active region and a second active region in the cell array region and the peripheral circuit region, respectively, but also a stack insulating layer including first, second and third insulating layers which are sequentially stacked on the first active region, and a gate insulating layer stacked on the second active region; forming a plurality of wordlines crossing over the stack insulating layer, and a gate electrode crossing over the gate insulating layer; and patterning at least the third and second insulating layers to form a charge storage layer and a blocking insulating layer which are sequentially stacked between the first insulating layer and the wordlines, wherein at least the second insulating layer is patterned so that the charge storage layer has a protruding part which protrudes from a sidewall of the wordlines.
 54. The method of claim 53, wherein the first and third insulating layers are made of silicon oxide, and the second insulating layer is made of silicon nitride.
 55. The method of claim 53, wherein the step of forming the device isolation layer, the stack insulating layer, the gate insulating layer, the wordlines, and the gate electrode includes the steps of: selectively forming the stack insulating layer on the substrate in the cell array region; selectively forming a gate insulating layer on the substrate in the peripheral circuit region; forming a lower gate conductive layer under a resultant structure including the gate insulating layer; sequentially patterning the lower conductive layer, the stack insulating layer, the gate insulating layer, and the substrate to form a trench area which defines a first active region and a second active region in the cell array region and the peripheral circuit region, respectively; forming a device isolation layer to fill the trench area; forming an upper gate conductive layer on an entire surface of a resultant structure including the device isolation layer; and forming a plurality of wordlines crossing over the upper gate conductive layer, and a gate electrode crossing over the second active region, wherein each of the wordlines includes an upper wordline crossing over the first active region, and a lower wordline intervened between the upper wordline and the first active region; and wherein the gate electrode includes an upper gate electrode crossing over the second active region, and a lower gate electrode intervened between the upper gate electrode and the second active region.
 56. The method of claim 53, wherein the step of forming the device isolation layer, the stack insulating layer, the gate insulating layer, the wordlines, and the gate electrode includes the steps of: forming a device isolation layer in a predetermined area of the substrate to define a first active region and a second active region in the cell array region and the peripheral circuit region, respectively; selectively forming first, second and third insulating layers in the cell array region of a resultant structure including the device isolation layer; forming a gate insulating layer on the second active region; forming a conductive layer on an entire surface of a resultant structure including the first to third insulating layers and the gate insulating layer; and patterning the conductive layer to form wordlines crossing the first active region and a gate electrode crossing the second active region.
 57. The method of claim 53, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: etching the third insulating layer by using the wordlines as an etch mask to form blocking insulating layers which are self-aligned to the wordlines; forming a first sidewall spacer on sidewalls of the wordlines, sidewalls of the blocking insulating layers, and the sidewall of the gate electrode; and etching the second insulating layer by using the wordlines and the first sidewall spacer as an etch mask to form a charge storage layer whose width is larger than a width of the wordline.
 58. The method of claim 57, further comprising a step of forming a gate capping oxide layer on surfaces of the wordlines and a surface of the gate electrode prior to formation of the first sidewall spacer.
 59. The method of claim 57, further comprising a step of implanting impurities into the second active region by using the gate electrode and the first sidewall spacer as an ion implanting mask to form a heavily doped source/drain region, before or after forming the charge storage layer.
 60. The method of claim 59, further comprising a step of implanting impurities into the first and second active regions by using the wordlines and the gate electrode as an ion implanting mask, before or after forming the blocking insulating layer.
 61. The method of claim 57, further comprising a step of forming a second sidewall spacer on the outer sidewall of the first sidewall spacer and the sidewall of the charge storage layer in the cell array region, and on an outer sidewall of the first sidewall spacer in the peripheral circuit region.
 62. The method of claim 61, further comprising a step of implanting impurities into the second active region by using the gate electrode, the first sidewall spacer, and the second sidewall spacer as an ion implanting mask to form a heavily doped source/drain region.
 63. The method of claim 62, further comprising a step of implanting impurities into the first and second active regions by using the wordlines and the gate electrode as an ion implanting mask to form a lightly doped source/drain region.
 64. The method of claim 62, further comprising a step of implanting impurities into the first and second active regions by using the wordlines, the gate electrode, and the first sidewall spacer as an ion implanting mask to form a lightly doped source/drain region.
 65. The method of claim 53, wherein the step of forming the charge storage layer and the blocking insulating layer includes the steps of: forming a first sidewall spacer on the sidewalls of the wordlines and the sidewall of the gate electrode; and sequentially etching the third and second insulating layers by using the gate electrode, the first sidewall spacer, and the first sidewall spacer as an etch mask to form a blocking insulating layer having a protruding part under the first sidewall spacer and a charge storage layer that is self-aligned to the blocking insulating layer.
 66. The method of claim 65, further comprising a step of a gate capping oxide layer on the surface of the gate electrode and the surfaces of the wordlines prior to formation of the first sidewall spacer.
 67. The method of claim 65, further comprising a step of implanting impurities into the second active region by using the wordlines, the gate electrode, and the first sidewall spacer as an ion implanting mask to form a heavily doped source/drain region, following formation of the first sidewall spacer.
 68. The method of claim 67, further comprising a step of implanting impurities into the first and second active regions by using the wordlines and the gate electrode as an ion implanting mask to form a lightly doped source/drain region, prior to formation of the first sidewall spacer.
 69. The method of claim 65, further comprising a step of forming a second sidewall spacer on the outer sidewall of the first sidewall spacer, the sidewall of the charge storage layer, and the sidewall of the blocking insulating layer in the cell array region, and on the outer sidewall of the first sidewall spacer in the peripheral circuit region.
 70. The method of claim 69, further comprising a step of implanting impurities into the second active region by using the gate electrode, the first sidewall spacer, and the second sidewall spacer as an ion implanting mask to form a heavily doped source/drain region.
 71. The method of claim of claim 70, further comprising a step of implanting impurities into the first and second active regions by using the wordlines and the gate electrode as an ion implanting mask to form a lightly doped source/drain region, prior to formation of the first sidewall spacer.
 72. The method of claim 70, further comprising a step of implanting impurities into the first and second active regions by using the wordlines, the gate electrode, and the first sidewall spacer as an ion implanting mask to form a light doped source/drain region, before or after forming the charge storage layer and the blocking insulating layer. 